A number of electrical connectors include a plurality of elongate conductors which electrically interconnect respective inputs and outputs of the connector. As known to those skilled in the art, an elongate conductor which is adjacent to or relatively near another elongate conductor will typically experience crosstalk. As explained in more detail hereinafter, crosstalk is generally defined as the unwanted coupling or transmission of an electrical signal from one pair of wires to another nearby pair of wires. Crosstalk occurs by inductive (magnetic field) coupling and by capacitive (electric field) coupling. In addition, increased levels of crosstalk are established between conductors which extend in a parallel or near-parallel relationship, such as the elongate conductors of many electrical connectors.
Crosstalk is generally undesirable as the integrity and definition of the signals transmitted via the conductor is impaired by the interfering coupled signals. In addition, the strength of the signals transmitted via the respective conductor is also typically reduced by the energy expanded or wasted in crosstalk, particularly at relatively high frequencies. Therefore, various methods have been employed to reduce or compensate for crosstalk, particularly within electrical connectors which include a plurality of elongate conductors.
For example, in a number of multi-conductor cables, the conductors are arranged in conductor pairs. In instances in which substantial capacitive and inductive coupling occurs between two pairs of conductors, crosstalk between the conductor pairs can reach an undesirable level. Thus, one goal in circuit design is to reduce the coupling between conductor pairs, such as by twisting the wire which forms each conductor pair or by separating the previously coupled conductor pairs. Notwithstanding the twisting of the wires of a conductor pair or the separation of the conductor pairs, crosstalk can still occur. This additional crosstalk typically results from the unbalanced nature of the conductors. More specifically, conductors are generally termed unbalanced in instances in which the coupling between a first conductor of a first conductor pair to each of the conductors and a second conductor pair is not equal.
This additional crosstalk can be reduced by requiring the coupling between the first conductor of the first conductor pair and both of the conductors of the second conductor pair to be equal. This additional crosstalk can be further reduced by requiring the coupling from the second conductor of the first conductor pair to both of the conductors of the second conductor pair to be equal and, furthermore, to be the same as a coupling between the first conductor of the first conductor pair and the conductors of the second conductor pair. As known to those skilled in the art, this balanced relationship can be represented by a bridge circuit having four nodes interconnected by capacitors, each having the same capacitance. Furthermore, this balanced relationship effectively reduces crosstalk since the signals coupled between the first and second conductor pairs will offset or cancel one another.
In a number of local area networks, however, the signals transmitted via the first and second conductors of a conductor pair are differential signals, that is, the signal on a first conductor of a conductor pair is the inverse or opposite of the signal on the second conductor of the conductor pair. Due to the inversion of the signals, each conductor of a conductor pair radiates a crosstalk signal having a different polarity. In order to reduce the crosstalk, the crosstalk signals radiated by the conductors of the first conductor pair must be equal to the crosstalk signals radiated by the conductors of a second conductor pair so as to cancel or offset without affecting the signal of the second conductor pair. In order to provide such cancellation or offsetting, the differential signals must be carefully adjusted in strength so that they will cancel or balance the nearby conductor pairs. By adding small amounts of capacitive coupling, the undesirable coupling can be balanced or compensated and the desired balanced or nulling effect can be achieved. However, the careful adjustment of the differential signals and the utilization of capacitive coupling generally increases the complexity of the multi-conductor cable and the signal transmission network.
One common type of connector is a 110-type connector which generally interconnects one or more connectors of a multi-conductor cable, such as a telecommunications cable, and a telecommunications device, such as a telephone, a computer or a facsimile machine. A 110-type connector can include a printed circuit board defining a predetermined number of conductive traces which provide an interface between the multi-conductor cable and the telecommunications device. A plurality of insulation displacement contacts are typically connected directly to respective conductive traces defined on the printed circuit board and are positioned to extend in a generally perpendicular direction to the surface of the printed circuit board. Each insulation displacement contact includes a pair of substantially planer, opposed blade portions which define an insulation displacement slot therebetween.
A 110-type connector also generally includes a plurality of spring contacts which are preferably connected to respective conductive traces defined on the printed circuit board and which extend laterally outward therefrom. Thus, a spring contact and an insulation displacement contact are generally connected to the opposed first and second ends of each conductive trace, respectively. The plurality of spring contacts are generally positioned within a modular jack housing or other data interface assembly which has an opening sized to receive a mating plug so as to thereby be electrically connected with the telecommunications device. Crosstalk between the conductive traces of a 110-type connector is controlled by minimizing or balancing magnetic loops which transmit the inductive component of the interfering signal and by minimizing or balancing the capacitive coupling which transmits the electric field component of the interfering signal.
In use, conductors of the multi-conductor cable are individually inserted into the insulation displacement slots defined by the respective insulation displacement contacts, such as with an impact tool. Common impact tools include those manufactured and sold by AT&T and Krone which have Model Nos. Harris-Dracon D-814 and LSA-PLUS #6417 2 055-01, respectively. More specifically, a predetermined force, typically a vertically downwardly directed force, must be applied, such as with an impact tool, to insert each conductor into the respective insulation displacement slot such that the insulating covering of the conductor is slit by the opposed blade portions and electrical contact is established with the conductor.
During application of the required insertion force, a 110-type connector must generally be supported by a firm surface to prevent relative movement of the 110-type connector and the resulting misalignment of the conductor and the respective insulation displacement contact. Thus, the conductors must generally be inserted into the respective insulation displacement slots prior to the insertion of the 110-type connector into a wall plate or face plate.
More specifically, a 110-type connector is typically inserted into a wall plate such that the opening defined through the wall plate to receive the mating plug is readily accessible, as known to those skilled in the art. Thus, the wall plate will not necessarily provide a firm support surface during the application of the insertion force since the printed circuit board of the connector generally extends perpendicular to the wall plate such that the insertion force is directed generally parallel to the wall plate. Accordingly, the wiring and rewiring of a 110-type connector is complicated since the connector is generally installed after inserting the conductors into the insulation displacement slots and must typically be removed from the wall plate prior to adding to or changing the wiring pattern.
Another electrical connector which has been developed to reduce crosstalk is described in U.S. Pat. No. 5,186,647 which issued Feb. 16, 1993 to W. John Denkmann, et al. and is assigned to AT&T Bell Laboratories (hereinafter the "'647 patent"). The high frequency electrical connector of the '647 patent includes a number of conductors mounted on a dielectric surface and extending in a generally parallel relationship for at least a portion of their length. At least one of the elongate conductors crosses the path of another conductor without making electrical contact therebetween to reduce the crosstalk between the conductors.
In particular, each elongate conductor of the high frequency electrical connector of the '647 patent includes a spring contact at a first end and an insulation displacement contact at a second end, opposite the first end. The elongate connectors are folded about a spring block and a cover is placed over and joined to the spring block to protect the conductive elements. The spring block includes a tongue-like portion which can be inserted into a jack frame which engages the cover to form a protective housing. The jack frame is adapted for insertion into a wall plate and includes an opening that is adapted to receive a modular plug for interconnecting a telecommunications device with the respective conductors of a multi-conductor cable.
Once the elongate conductors of the electrical connector of the '647 patent have been folded about the spring block and the cover has been placed thereover, the conductors of a multi-conductor cable can be individually inserted into the insulation displacement slots defined by the respective insulation displacement contacts, such as with an impact tool. As explained above in conjunction with other 110-type connectors, the electrical connector must generally be supported by a relatively firm surface during insertion of the conductors into the respective insulation displacement slots in order to prevent relative movement of the electrical connector and to maintain alignment of the conductors with respect to the insulation displacement slots.
In addition, due to the folding of the insulation displacement contacts of the high frequency electrical connector of the '647 patent about the sidewalls of the spring block, the force required to insert the conductors into respective insulation displacement contacts is directed generally parallel to the wall plate in which the jack frame is mounted. Therefore, the wall plate does not generally provide a sufficiently firm surface to support the electrical connector during insertion of the conductors in the respective insulation displacement slots. Thus, the conductors must also be generally inserted into respective insulation displacement slots prior to mounting the jack frame into the wall plate thereby complicating the wiring and rewiring of the electrical connector since the jack frame must be removed from the wall plate prior to adding to or changing the wiring pattern.
As is also known to those skilled in the art, the conductive elements of the modular plug which are received by the modular jack of the high frequency electrical connectors of the '647 patent are arranged in a first predetermined order. In addition, the conductors of the multi-conductor cable are generally arranged in conductor pairs, referred to as balanced pairs. Each balanced or conductor pair forms one circuit of a data or telephone transmission path. Crosstalk or interference between adjacent circuits in the same cable is undesirable. The conductor pairs are typically color-coded such that a technician can identify the individual conductors of each conductor pair. The conductor pairs are also generally twisted to further reduce crosstalk between the conductor pairs. In order to ensure that predetermined conductors of the multi-conductor cable are electrically connected to predetermined conductive elements of the plug, each conductor of the multi-conductor cable must be inserted into a predetermined insulation displacement slot.
The high frequency electrical connector of the '647 patent, however, does not arrange the insulation displacement contacts such that the predetermined insulation displacement slots in which each conductor of a conductor pair is inserted are adjacent. Thus, end portions of the conductors of the multi-conductor cable must be un-twisted in order to be inserted in the predetermined insulation displacement slots. By un-twisting at least an end portion of the conductors, crosstalk between the conductor pairs increases. Further, by requiring the conductors of a conductor pair to be inserted in remote, i.e., non-adjacent, insulation displacement slots, a technician must pay increased attention to the conductors to ensure that the conductors are inserted in the proper insulation displacement contact slots. Accordingly, the efficiency or speed with which an electrical connector is wired or rewired is diminished.